Inspection systems have traditionally had difficulty determining the presence or absence of transparent or specular objects. As an example, pills, tablets, and capsules that are transparent or specular and included in packaging, such as blister packaging produced by blister packer machines, are to be inspected to ensure that a pill is appropriately contained in a blister or compartment of the packaging for quality control purposes. Heretofore, such automated inspection has been difficult due to the transparent or specular nature of such pills.
Inspections on two-dimensional images, either color or grayscale, cannot effectively discriminate between empty compartments and compartments with transparent pills because intensities with and without transparent pills are similar. Three-dimensional inspection systems may be more successful than two-dimensional inspection systems, but blister packages are typically carried on a conveyor belt at high speeds, such that it is difficult to achieve high resolution reconstructions with typical camera equipment in sufficient time to operate in high production rate environments.
As understood in the art, noise from imaging tends to degrade inspection processes. Hence, designers of conventional image inspection systems use various techniques for reducing optical and other noise.